Effect of tooth surface roughness on marginal seating and retention of complete metal crowns

STATEMENT OF PROBLEM: Retention and marginal adaptation factors have major influence on the failure of cemented complete veneer crowns. PURPOSE: This study investigated the effect of axial surface roughness on the marginal seating and retention of silver-palladium crowns luted with zinc phosphate, glass ionomer, and resin cements. MATERIAL AND METHODS: Coarse and fine diamond stones were used to create various surface roughnesses of premolars. A milling machine was used to control the height and angle of the axial walls of tooth preparations. Ten cast metal crowns in 6 subgroups were luted with 3 cements (Phosphacap, Fuji Cap I, and Panavia 21). Marginal seating was recorded with a Digimatic indicator. Retention was determined by measuring the tensile force required to remove a metal crown with a Lloyd testing machine. RESULTS: Two-way analysis of variance revealed statistically significant differences (P <.001) in retention for both luting cements and surface roughness. No significant difference was recorded for marginal seating relative to roughness (P =.860) and interaction effects (P =.204). Tukey-HSD tests revealed substantial differences in retention among Phosphacap, Fuji Cap I, and Panavia 21 cements. Significant differences were not confirmed in marginal seating between Fuji Cap I and Phosphacap cements with coarse diamonds, and Phosphacap and Panavia 21 cements with fine diamonds. CONCLUSIONS: The best retention for complete metal crown was demonstrated for tooth preparations ground with coarse diamonds and cemented with Panavia 21 cement. Differences in axial surface roughness had no effect on the marginal seating of the complete metal crowns.     

Panavia/sandblasted resin bonded prostheses: a five year retrospective study

The authors feel that this study suggests that the Panavia/sandblasted retention method, with its low debond rate, is a viable method for luting resin bonded prostheses. The authors wish to acknowledge the services of Ms. Jane Jakobsen (statistician) and Ms. Connie Norton (secretary) who made significant contributions to the completion of this article. Their help was much appreciated.     

Effect of Sandblasting on Interfacial Contact Behavior of Carbon-Fiber-Reinforced Polymer-Metal Couples

This paper presents the results of a study that was conducted on the sliding behavior of a carbon-fiber-reinforced polymer rod in contact with copper or aluminum sleeves simulating the components of a wedge anchor system. The influence of sandblasting the metal sleeves was related to the displacement and shear stress of the couple for different contact pressures. In general, the interfacial shear stress was found to increase linearly with contact pressure. However, the highest interfacial shear stresses were recorded when sandblasted soft annealed sleeves were used. This effect was the result of a larger contact area which increased the strength of the interface.     

Retention of paraposts cemented with dentin-bonded resin cements

The main purpose of this study was to assess the retention of Paraposts cemented with dentin-bonded resin cements in single-rooted teeth with elliptical canals. Forty-two mandibular premolars and canines were used in this study. The crowns of these teeth were removed 1 mm above the cementoenamel junction and the root canals instrumented to a depth of 8 mm to receive size 5 Paraposts. Prepared teeth were divided into six equal groups. Each group was assigned to a different cementation system at random. The six cementation systems used were: Fleck's Cement, Universal Post Cementation Kit, Prisma Universal Bond 3/Biomer, Scotchbond 2/Resiment, All-Bond 2/All-Bond C & B Cement, and Scotchbond Multi-Purpose/Resiment. Following post cementation, the teeth were stored in water at 37 degrees C for 24 hours, after which the posts were subjected to uniaxial tensile force on a testing machine until post separation occurred. Paraposts cemented with Prisma Universal Bone 3/Biomer or with Scotchbond Multi-Purpose/Resiment had significantly greater separation forces than posts cemented with any of the other cementation systems. Adhesive failure of the posts occurred in all of the specimens of the resin cement groups, whereas cohesive failure of the cement occurred in the majority of the specimens of the zinc phosphate cement group. The effects of thermocycling and post length (5 mm versus 8 mm) on the retention of Paraposts cemented with dentin-bonded resin cements were also investigated. Neither thermocycling nor post length had a significant effect on post separation force.     

Correction factors for water-proofing sleeves in kilovoltage x-ray beams

This paper investigates the effect of the waterproofing sleeve on the calibration of kilovoltage photon beams (50-300 kV). The sleeve effect correction factor, ps has been calculated using the Monte Carlo method as the ratios of the air kerma in an air cavity of a cylindrical chamber without the waterproofing sleeve to that with a sleeve. Three sleeve materials have been studied, PMMA, nylon and polystyrene. The calculations were carried out using the EGS4 (Electron Gamma Shower version 4) code system with the application of a correlated-sampling variance-reduction technique. The results show that the sleeve correction factor for 1-mm thick nylon and polystyrene sleeves, ps varies from 0.992 to 1.000 and from 0.981 to 1.000, respectively, for the same beam quality range. The ps factor varies with sleeve thickness, beam quality and phantom depth. No significant dependence of the ps factor on field size and source-surface distance has been found. Measurements for PMMA, nylon and polystyrene sleeves of various thicknesses have also been carried out and show excellent agreement with Monte Carlo calculations.     

Synergism of capillary isotachophoresis and capillary zone electrophoresis

Commercially pure titanium (CPT) substrate was subjected to porcelain firing and bond strengths under three-point bending mode (span length: 15 mm; crosshead speed: 0.5 mm/min) were evaluated. Experimental variables included surface treatments of CPT and porcelain firing schedules. Variables for the surface treatments were (1) sandblasting, (2) mono- and triple-layered nitridation, and (3) mono-layered chrome-doped nitridation. Variables for the porcelain firing schedule included (4) bonding agent application, (5) bonding agent plus gold bonding agent application, and (6) Procera porcelain application. All together eleven sample groups were prepared with different combination of aforementioned experimental variables. Statistically all of them exhibited no significant differences. Hence, we employed two further criteria; (I) the minimum bond strength should exceed the maximum porcelain strength per se, and (II) the CPT substrate should not be heated close to the beta-transus temperature. After applying these criteria, it was concluded that mono-layered nitridation and mono-layered application of chrome-doped nitridation on both (with and without) sandblasted and non-sandblasted surfaces were the most promising conditions for a successful Titanium-Porcelain System.     

Mechanical Behavior of CFRP Rod Anchors under Tensile Loading

This paper presents the results of an experimental and numerical study to examine the mechanical behavior of carbon fiber reinforced polymer rods gripped by a wedge anchor, comprised of an aluminum sleeve, four stainless steel wedges, and a stainless steel barrel. The carbon fiber reinforced polymer rod-anchor system was tested under monotonic and cyclic loading conditions. In the static load tests, the effect of presetting loads, usage history, and sleeve material were investigated. Presetting load levels of 50, 65, 80, and 100 kN were used, and tests were conducted with new and reused anchors. Aluminum and copper sleeves were considered. As the presetting load increased, the displacement (or slip) of the rod and sleeve decreased. No significant effect of reusing the anchor was found other than replacing the sleeve. Anchors with copper sleeves performed poorly at low presetting loads, in comparison to aluminum sleeves. Cyclic load tests were conducted on anchors using aluminum sleeves with a presetting load of 80 kN. The effects of cycling on the rod and sleeve displacement were minor for different mean stresses and stress ratios. A finite-element model, consisting of three contact surfaces, was applied to simulate the anchor components; the displacement of the rod compared well with experimental results.     

Race, life style and renal disease in South Africa

PURPOSE: Clinical evaluation of repairing old amalgam restorations using composite inlays cemented with two different bonding agents. MATERIALS AND METHODS: Occluso-proximal Class II inlay cavities were prepared in 50 old defective amalgam restorations. Extra oral system (EOS) composite inlays were cemented with two different bonding agents (All-Bond 2 or Geristore). After final finishing and polishing of each restoration, evaluation was carried out at baseline, 6 months, 12 months, and 24 months using US Public Health Service criteria. The data were collected and statistically analyzed using Chi-square test. RESULTS: No significant difference was found between the two bonding materials at any time interval.     

Vertical mammaplasty as secondary surgery after other techniques

The effect of ultrasonic insertion on the filler content and the gap width for two brands of composite resin luting agents, intended for luting with the ultrasonic insertion technique, were studied after MOD ceramic inlays (Cerec) had been placed. In addition, the internal and marginal gap widths were determined after MOD ceramic inlays (Celay) bad been luted on extracted premolars with this technique. No statistically significant differences (P > 0.05) were observed for either brand between the filler content obtained from the internal surfaces, from the excess luting agent, or from the luting agent as delivered. There were no statistically significant differences (P > 0.05) between the final internal and marginal gap widths when the two brands of luting agent were compared with each other. Except for the final occlusal and internal gap widths obtained for the inlays luted with the Sono-Cem luting agent, no statistically significant differences (P > 0.05) were observed between the gap widths at the different locations determined. Thus, the ultrasonic insertion technique used did not significantly influence the filler ratio of the hybrid luting agents studied. Judged by the findings in this study, the properties of luting agents seem to greatly influence the final marginal and internal gap widths.     

Contraction gaps in Class II restorations with self-cured and light-cured resin composites

PURPOSE: To evaluate in vitro the cervical gap formation in composite restorations in which an increment of autopolymerizing composite was interposed between the light-cured filling material and the dentin bonding system. Two different self-cured materials and two different adhesives were used and compared. MATERIALS AND METHODS: In 40 Class II cavity preparations with the gingival margins in dentin or cementum, an increment of either of two different autopolymerizing composites, Palfique or Bisfil 2B, was interposed between the light-cured filling material (Palfique Estelite) and either of two different dentin bonding systems, All-Bond and Superbond D (20 restorations each). The specimens were immersed in toluidine blue dye. A section was taken from each specimen and examined under an optical microscope. The extent of dye penetration was measured. The specimens were then stored in water for 1-4 months and replicas of the sections were examined by SEM. RESULTS: Good marginal adaptation was observed for All-Bond/Bisfil 2B in all the restorations. All-Bond/Palfique showed good adaptation in 7 out of 10 cases, the failures occurring between bonding agent and composite. Superbond D/Palfique and Superbond D/Bisfil 2B showed marginal gap formation in 8 out of 10 and in all the restorations respectively. In the latter, four gaps occurred between bonding agent and dentin. As a consequence, a very significant difference (P<0.001) was found between All-Bond and Superbond treatments; no significant difference was found between Bisfil 2B and Palfique in each group treated with either All-Bond or Superbond. After 1-4 months storage in water, hygroscopic expansion of the restorative materials reduced the total number of gaps and the efficacy of the treatments was no more significantly different.     

Effect of Surface Texturing on CPT Friction Sleeve Measurements

As the use of the cone penetration test (CPT) has increased for geotechnical site characterization, significant research has been performed to identify and control the factors that affect the tip (qc), sleeve (fs), and pore pressure (u) measurements. However, a number of factors that affect the friction sleeve have yet to be understood, appreciated, and accounted for in penetrometer designs. This paper highlights a number of these issues, with specific attention centered on the effect of surface texturing on the friction sleeve measurement. An understanding of the role of surface roughness on soil-geomaterial interfaces provides a framework for analyzing the effect on the friction sleeve measurement and could provide a basis to improve its design. A series of CPT soundings were performed in the southeast United States with conventional smooth and textured friction sleeves. Results indicate that friction measurements with a textured sleeve are 70% greater on average than the value obtained with a conventional smooth friction sleeve in sand and provide a basis for developing new design procedures where interface values are required.     

Long term clinical evaluation of three luting materials

A last critical step in the completion of a cast restoration is permanent cementation. With the development of new luting agents the practitioner has to be aware of the physical and biological properties as well as the long term clinical performance of these materials. In this study three commonly used luting agents were evaluated over a four year period. The three cements, a zinc phosphate, a glass ionomer and a resin cement were tested for their reaction to periodontal tissues, pulpal response and other clinical parameters. In twenty six patients, 61 crowns, onlays or bridge abutments were cemented. Evaluations were made at 0 hour, after 7 days, 6 and 12 months and 4 years. In general the cements performed satisfactorily. Health of periodontal tissues adjacent to the crowns improved considerably after 7 days. Postcementation hypersensitivity appeared to be a negligible problem, which was attributed to the time span between preparation and cementation, which exceeded in most instances four weeks. The choice of a final luting agent should be based on anticipated postoperative pulpal reactions, rather than exclusive reliance on physical properties.     

Mutagenicity and DNA-damaging activity of decomposed products of food colours under UV irradiation

Five synthetic food colours Food Red Nos 3, 40 and 102 and Food Blue Nos 1 and 2, and their UV irradiated products were tested for mutagenic activity by means of the Ames test using Salmonella typhimurium strains TA98 and TA100. Food colours were irradiated with UV light for 14 days. Food Red Nos 3, 40 and 102 and Food Blue No. 1 were non-mutagenic before and after irradiation. UV irradiated products of Food Blue No. 2 were mutagenic in TA98 with or without S-9 mix. The mutagenic activity increased with increasing irradiation period, reached maximum potency on day 6, and then decreased. Moreover, Food Blue No. 2 showed DNA-damaging activity after 14 days of irradiation in rec-assay using Bacillus subtilis strains H17 and M45. The capillary electrophoresis was applied for the analysis of UV irradiated products of Food Blue No. 2. The original peak of Food Blue No. 2 was decomposed into seven peaks after UV irradiation.     

Phage typing combined with pulsed-field gel electrophoresis and random amplified polymorphic DNA increases discrimination in the epidemiological analysis of Salmonella enteritidis strains

In adult rabbits, mid-diaphyseal segments of the radius or ulna were excised to produce defects greater than the critical size for spontaneous bone repair. The defects were enveloped in sleeves composed of nonbiodegradable expanded polyfluoroethylene (ePTFE), pore size 30, 60, 90 microns, and compared with sleeves of three biodegradable materials. Bone morphogenetic protein and associated noncollagenous bone matrix protein (BMP/NCP) or recombinant human morphogenetic protein (rhBMP-2) were implanted inside the sleeves. Albumin was implanted for a control system. Without intracompartmental BMP, only about 10%-15% of the defect was repaired by bone growth extending from the bone ends into the sleeves composed of ePTFE, pore size 30 microns. With sleeves with pore size 60 or 90 microns and intracompartmental BMP/NCP, 54%-96% regeneration occurred within 8 weeks after the operation. Sleeves of biodegradable nonimmunogenic materials such as polyorthoester (POE) and polylactic-polyglycollic acids (PLA/PGA) permitted 86%-98% restoration of bone continuity, but only when BMP was present in the lumen. With puncture holes (0.5 mm in diameter), implants of BMP/NCP in the 30-micron PTFE sleeve produced transmembrane external callus formation and bone regeneration to 147%. Sleeves composed of aorta first calcified, then induced complete intracompartmental bone regeneration. Atelocollagen sleeves incited a low-grade inflammatory cell reaction and did not promote complete regeneration. Under conditions presently undisclosed segments of the ulna bridged with ePTFE, were incompletely paired, even with intracompartmental BMP/NCP. Puncture holes of 0.5 mm admitted ingrowth of capillaries and introduced local conditions favorable for the response to BMP/NCP. BMP/NCP may promote proliferation of nutrient vessels and differentiation of bone marrow stroma cells between the open bone ends. For further investigation, the hypothesis to be examined is that the optimum response to BMP/NCP and rhBMP-2 would emerge in compartments containing first a high concentration gradient and second proliferating perivascular cells.     

A new tool to measure pressure under burn garments

This article introduces a new tool to measure the pressure that is under pressure garments. The Iscan (Tekscan, Inc.) system uses a patented ultra-thin (0.007 inch) sensor with multiple sensing locations that sample continuously at 100 times per second. It is noninvasive, convenient, and quick. The study had two parts. First, we established the validity and reliability of the device. Next, garment/scar interface pressures were measured on new garments with use of the Iscan system. Four garment types were studied, with 10 measurements made in each group: Isotoner gloves (Smith & Nephew Roylan, Inc.); custom-fit pressure gloves; Tubigrip forearm sleeves (Seton Health Care Group); and custom-fit pressure forearm sleeves. Mean garment/scar interface pressures were 18 +/- 2 mm Hg for the Isotoner glove, 34 +/- 5 mm Hg for the custom-fit pressure glove, 20 +/- 7 mm Hg for the Tubigrip sleeve, and 35 +/- 6 mm Hg for the custom-fit sleeve. We concluded that the Iscan system can be used to measure pressure under pressure garments accurately and reliably, and that custom-fit hand and forearm garments provide more pressure than Isotoner gloves or Tubigrip sleeves.     

Lumbar MR myelography in the prone position: evaluation of nerve root sleeve delineation

Although MR myelography is able to depict the subarachnoid space noninvasively, its ability to depict the nerve root sleeve is poor. The authors placed subjects in the prone position to increase the volume of spinal-fluid within nerve root sleeves and improve their depiction in MRM. MRM images of five normal volunteers taken in the supine and prone positions were visually correlated. Improved delineation of nerve root sleeves was obtained in all subjects.     

Histological changes induced by CO2 laser microprobe specially designed for root canal sterilization: in vivo study

Sixty-six class-II CAD/CAM-manufactured ceramic inlays (Cerec) were placed in 27 patients. Each patient received at least one inlay luted with a dual-cured resin composite and one inlay luted with a chemically cured resin composite. The inlays were examined 5 years after luting using the California Dental Association (CDA) criteria. Eighty-nine percent of the 66 inlays were rated 'satisfactory'. During the follow-up period replacement was required for 3 inlays because of inlay fractures (4.5%) and 1 inlay because of fracture of the tooth substance (1.5%). All those inlays were luted with the dual-cured resin composite luting agent. Of the remaining 62 inlays the CDA rating 'excellent' was given to 84% for color, 97% for surface, and 81% for anatomic form. 'Excellent' margin integrity was seen in 52% of the dual-cured resin composite luted inlays and in 61% of the chemically cured resin composite luted inlays. No statistically significant (P> 0.05) difference was observed between the two luting agents.     

Fibromyalgia: from information to questions

A previous study has shown that sandblasting and silane priming a post-cured inlay resin gave a secure bond to dual-cure luting resin. To determine the influence of salivary contamination 4 additional groups of 15 post-cured resin discs were mounted in acrylic cylinders, their faces sandblasted with 50 microns alumina and silane primed. Surface treatments with saliva (sa), air/water spray (a/w), phosphoric acid gel (pa), and silane (si) followed in the order listed: A) control, no further treatment; B) sa, a/w; C) sa, a/w, si; D) sa, a/w, pa a/w; E) sa, a/w, pa, a/w, si. A 3.9 mm diameter column of dual-cure resin lute was then bonded to the dry stored in water surfaces. Specimens were stored in water for 2 weeks after which the dual-cure resin columns were sheared off the post-cured resin discs. Shear bond strengths were A) 19.2 +/- 3.7, B) 17.4 +/- 3.9, C) 16.7 +/- 3.1, D) 15.6 +/- 3.5, E) 15.4 +/- 2.3 MPa. One-way ANOVA and Duncan's Multiple Range Procedure showed groups D and E to be significantly lower than the uncontaminated control group A (p < 0.05). There were 2 adhesive failures in group B and all others were cohesive within the post-cured resin discs. This implies that air/water alone after salivary contamination is an unreliable cleansing method. The low shear bond values for Groups D and E may have been related to inadequate clearance of the phosphoric acid gel. It was concluded that salivary contamination adversely affected the quality of the bonds studied and decontamination using phosphoric acid gel resulted in significantly reduced shear bond strengths.     

Microleakage of new dentin bonding systems using human and bovine teeth

The objective of this study was twofold: to evaluate the microleakage behavior of three dentin bonding systems and to determine if bovine teeth are comparable substrates to human teeth when studying the microleakage of various materials. The materials evaluated were Scotchbond Multi-Purpose Adhesive, Prisma Universal Bond 3, and All-Bond 2. All three bonding systems were used in combination with Prisma APH hybrid composite for comparison of microleakage behavior. Sixty class 5 preparations were cut at the cementoenamel junction for groups containing 30 human and 30 bovine teeth. A 1 mm 45 degree bevel was placed at the enamel margin. Teeth were grouped according to the dentin bonding system used and then restored according to the manufacturer's directions. After restoration, the teeth from each group were stored in distilled water at 37 degrees C for 3 days. The teeth were then thermocycled between 4 degrees C and 58 degrees C for 100 cycles and returned to distilled water at 37 degrees C for an additional 4 days. The teeth were then sealed with nail polish up to 1 mm from the margins of the restoration and placed in 45Ca isotope for 2 hours. The teeth were then sectioned and placed on x-ray film to produce autoradiographs. Microleakage was evaluated for the enamel and dentin margins separately using the following scale: 0 = no leakage, 1 = penetration of isotope to less than 1/2 the distance to the axial wall, 2 = penetration of isotope greater than 1/2 of the distance to the axial wall but short of the axial wall, and 3 = penetration of isotope to the axial wall or beyond. The materials were compared to each other using the Mann-Whitney U and Kruskal-Wallis tests. The gingival margins were compared to the incisal margins for all materials. No statistically significant differences in microleakage were revealed between the incisal and gingival location for human substrates, but there was statistically significant greater gingival microleakage for bovine substrates. All-Bond 2 leaked significantly more than Scotchbond Multi-Purpose for human substrates at the incisal margin. All-Bond 2 had significantly more microleakage than Prisma Universal Bond 3 at both dentin and enamel margins for the bovine substrate. There were no statistically significant differences in microleakage among the bonding systems for the human substrate. No statistically significant differences between the microleakage behavior of human and bovine substrates were found. These results support the use of bovine teeth for in vitro microleakage studies.     

Considerations on the Kaufman approach to binary phase diagram calculation

The Kaufman approach to phase equilibria involving primarily the fcc, bcc and hcp phases was examined outside the Group Nos. 4 to 10 range where it is customarily employed. The “stability parameters” (ΔH and ΔS of transformation) for most elements in the Group Nos. 1 to 3 region were found to fit satisfactorily the correlation curves of stability parametervs group no.; some of the parameters for Al, Be, Mg and Ti, however, did not. The rare earth parameters fit well in the Group No. 3.5 position they were expected to occupy. A sample phase diagram calculated between two Group 1 elements was in good agreement with experiment. Phase boundaries of fcc +bcc regions adjacent to terminal solid solutions in several Group 1/Group 2 and Group 1/Group 3 systems, on the other hand, were quite unsatisfactory. This difficulty was traced to the high, positive regular solution constants calculated for both phases. Such constants were shown to result from the downward concavity of a plot of enthalpy of vaporizationvs Group No. in the Nos. 1 to 3 region; in the Nos. 4 to 10 range this plot is concave upward.